Several points moving randomly in a circle.
This is a solution to the question raised in R-help: https://stat.ethz.ch/pipermail/r-help/2008-December/183018.html.
library(animation)
ani.options(interval = 0.1, nmax = 100)
par(mar = rep(0.5, 4))
BM.circle(cex = 2, pch = 19)